
Generic Polygon Clipper (gpc) Revision History
==============================================


v2.31    4th Jun 1999
---------------------
    Separated edge merging measure based on a user-defined GPC_EPSILON
    value from general numeric equality testing and ordering, which now
    uses direct arithmetic comparison rather an EPSILON based proximity
    test.
    Fixed problem with numerical equality test during construction of
    local minima and scanbeam tables, leading to occasional crash.
    Fixed hole array memory leak in gpc_add_contour.
    Fixed uninitialised hole field bug in gpc_polygon_clip result.

v2.30   11th Apr 1999
---------------------
    Major re-write.
    Minor API change: additional 'hole' array field added to gpc_polygon
    datatype to indicate which constituent contours are internal holes,
    and which form external boundaries.
    Minor API change: additional 'hole' argument to gpc_add_contour
    to indicate whether the new contour is a hole or external contour.
    Minor API change: additional parameter to gpc_read_polygon and
    gpc_write_polygon to indicate whether or not to read or write
    contour hole flags.
    Fixed NULL pointer bug in add/merge left/right operations.
    Fixed numerical problem in intersection table generation.
    Fixed zero byte malloc problem.
    Fixed problem producing occasional 2 vertex contours.
    Added bounding box test optimisations.
    Simplified edge bundle creation, detection of scanbeam internal
    edge intersections and tristrip scanbeam boundary code.
    Renamed 'class' variable to be C++ friendly.

v2.22   17th Oct 1998
---------------------
    Re-implemented edge interpolation and intersection calculations
    to improve numerical robustness.
    Simplified setting of GPC_EPSILON.

v2.21   19th Aug 1998
---------------------
    Fixed problem causing occasional incorrect output when processing
    self-intersecting polygons (bow-ties etc).
    Removed bug which may lead to non-generation of uppermost triangle
    in tristrip output.

v2.20   26th May 1998
---------------------
    Major re-write.
    Added exclusive-or polygon set operation.
    Replaced table-based processing of edge intersections with
    rule-based system.
    Replaced two-pass approach to scanbeam interior processing with
    single pass method.

v2.10a  14th May 1998
---------------------
    Minor bug-fixes to counter some v2.10 reliability problems.

v2.10   11th May 1998
---------------------
    Major re-write.
    Incorporated edge bundle processing of AET to overcome coincident
    edge problems present in previous releases.
    Replaced Vatti's method for processing scanbeam interior regions
    with an adapted version of the scanbeam boundary processing
    algorithm.

v2.02   16th Apr 1998 (unreleased)
----------------------------------
    Fixed internal minimum vertex duplication in gpc_polygon_clip
    result.
    Improved line intersection code discourage superfluous
    intersections near line ends. 
    Removed limited precision number formatting in gpc_write_polygon.
    Modification to allow subject or clip polygon to be reused as the
    result in gpc_polygon_clip without memory leakage.

v2.01   23rd Feb 1998
---------------------
    Removed bug causing duplicated vertices in output polygon.
    Fixed scanbeam table index overrun problem.

v2.00   25th Nov 1997
---------------------
    Major re-write.
    Replaced temporary horizontal edge work-around (using tilting)
    with true horizontal edge handling.
    Trapezoidal output replaced by tristrips.
    gpc_op constants now feature a `GPC_' prefix.
    Data structures now passed by reference to gpc functions.
    Replaced AET search by proxy addressing in polygon table.
    Eliminated most (all?) coincident vertex / edge crashes.

v1.02   18th Oct 1997 (unreleased)
----------------------------------
    Significantly reduced number of mallocs in build_lmt. 
    Scanbeam table now built using heapsort rather than insertion
    sort.
   
v1.01   12th Oct 1997
---------------------
    Fixed memory leak during output polygon build in
    gpc_clip_polygon.
    Removed superfluous logfile debug code.
    Commented out malloc counts.
    Added missing horizontal edge tilt-correction code in
    gpc_clip_polygon.
   
v1.00   8th Oct 1997
--------------------
    First release.

